Frequency-hop transmission for satellite packet switching and terrestrial packet radio networks

The performance of frequency-hop transmission in a packet communication network is analyzed. Satellite multiple-access broadcast channels for packet switching and terrestrial packet radio networks are the primary examples of the type of network considered. An analysis of the effects of multiple-access interference in frequency-hop radio networks is presented. New measures of "local" performance are defined and evaluated for networks of this type, and new concepts that are important in the design of these networks are introduced. In particular, error probabilities and local throughput are evaluated for a frequency-hop radio network which incorporates the standard slotted and unslotted ALOHA channel-access protocols, asynchronous frequency hopping, and Reed-Solomon error-control coding. The performance of frequency-hop multiple access with error-control coding is compared with the performance of conventional ALOHA random access using narrow-band radios.     

Wormhole-Based Antijamming Techniques in Sensor Networks

Due to their very nature, wireless sensor networks are probably the category of wireless networks most vulnerable to "radio channel jamming"-based denial-of-service (DoS) attacks. An adversary can easily mask the events that the sensor network should detect by stealthily jamming an appropriate subset of the nodes; in this way, he prevents them from reporting what they are sensing to the network operator. Therefore, even if an event is sensed by one or several nodes (and the sensor network is otherwise fully connected), the network operator cannot be informed on time. We show how the sensor nodes can exploit channel diversity in order to create wormholes that lead out of the jammed region, through which an alarm can be transmitted to the network operator. We propose three solutions. The first is based on wired pairs of sensors, the second relies on frequency hopping, and the third is based on a novel concept called uncoordinated channel hopping. We develop appropriate mathematical models to study the proposed solutions     

Performance analysis of spread spectrum packet radio network withchannel load sensing

A continuous-time Markov-chain model for an asynchronous communication spread-spectrum code-division-multiple-access (CDMA) packet radio network is developed. The network is composed of mutually independent users. The receiver-based code is considered; a terminal with a packet to send looks up the destination's code and transmits on that code. Each user senses the channel load and refrains from transmission if the channel load exceeds the channel threshold. The model makes it possible to study the threshold effect of channel load on the performance of the CDMA packet radio network. Improvements in performance of spread-spectrum packet radio networks due to channel-load sensing are shown. Steady-state results for throughput are obtained     

CDMA随机多址接入技术研究

CDMA作为一种多址接入技术在无线网络中已广为应用,在多码CDMA和单码CDMA研究的基础上,构造了多码CDMA和单码CDMA在无线分组数据网络中的随机多址接入模型,并且分析了两种系统的吞吐率特性和归一化时延特性。结果证明单码CDMA和多码CDMA具有相同的多址接入性能。     

一种针对超短波电台接入网的混合信道接入方案

为超短波电台接入网提供了一种混合信道接入方案,方案借鉴了民用接入技术的一些先进理念,并结合军用跳频电台网络的特殊业务应用需求,采用了一种静态TDMA、动态TDMA和频分多址FDMA的混合信道接入策略,实现了多用户多业务传输的QOS保障,满足了军用业务的特殊传输需求。     

Making transmission schedules immune to topology changes inmulti-hop packet radio networks

Transmissions scheduling is a key design problem in packet radio networks, relevant to TDMA and CDMA systems. A large number of topology-dependent scheduling algorithms are available, in which changes of topology inevitably require recomputation of transmission schedules. The need for constant adaptation of schedules to mobile topologies entails significant, sometime insurmountable, problems. These are the protocol overhead due to schedule recomputation, performance penalty due to suspension of transmissions during schedule reorganization, exchange of control message and new schedule broadcast. Furthermore, if topology changes faster than the rate at which new schedules can be recomputed and distributed, the network can suffer a catastrophic failure. The authors propose a robust scheduling protocol which is unique in providing a topology transparent solution to scheduled access in multi-hop mobile radio networks. The proposed solution adds the main advantages of random access protocols to scheduled access. Similarly to random access it is robust in the presence of mobile nodes. Unlike random access, however, it does not suffer from inherent instability, and performance deterioration due to packet collisions. Unlike current scheduled access protocols, the transmission schedules of the proposed solution are independent of topology changes, and channel access is inherently fair and traffic adaptive     

Delay and throughput characteristics of TH, CDMA, TDMA, and hybridnetworks for multipath faded data transmission channels

The new concepts of adaptive time hopping and variable frame code division (CDMA) multiple access are introduced. By a unified analysis, the probabilities of bit and packet errors in multipath fading environment for five time division (TDMA), code division, and time hopping (TH) related multiaccess networks are obtained; namely, TDMA, CDMA, CDMA/TDMA, Adaptive CDMA/TH, and variable frame CDMA/TDMA networks. The delay and useful throughputs of the five systems are also evaluated for data and voice traffic. All systems compared have the same channel power and bandwidth and support the same traffic. Though implementation issues are not covered, CDMA systems are put at a disadvantage (compared to cellular-type FDMA networks, for example) by ignoring such inherent advantages as voice silence utilizations and automatic frequency reuse. Nontheless, two CDMA systems outperform TDMA systems at low and medium input traffics     

Performance analysis of hybrid ARQ protocols in a slotteddirect-sequence code division multiple-access network: jamming analysis

An examination is made of the performance of type-I hybrid ARQ (automatic repeat request) protocols in a slotted direct-sequence CDMA (code-division multiple access) network operating in a hostile jamming environment. The network consists of an arbitrary number of transceivers arranged in a paired-off topology. The traffic arrival process is derived by means of a Markov model. Throughput-delay expressions are derived in terms of the channel cutoff rate and capacity. The effects of jammer state information are discussed. Network design parameters are identified and their dependency on system parameters is examined in detail. It is shown that, for a given population size, traffic intensity, and bit energy/jammer noise ratio, there is an optimal probability of retransmission, code rate, and processing gain that maximizes network performance in the presence of worst-case pulse jamming     

Packet data over cellular networks: the CDPD approach

Cellular digital packet data is a mobile packet data technology that operates on the spectrum assigned to a telephone cellular network, such as the Advanced Mobile Phone Service. This article undertakes a thorough survey of the CDPD radio interface and explores the main functional layers of this interface. Specifically, it extensively studies the physical layer, the data link layer, and the subnetwork-dependent convergence protocol, and explains their semantics and functional characteristics. Furthermore, it emphasizes several significant aspects such as the medium access procedure, the forward and reverse channel configurations, the data multiplexing scheme, and the channel hopping procedure     

Packet-length adaptive CLSP/DS-CDMA: performance in burst-error correlated fading channels

The authors analyze throughput-delay performance of an unslotted channel load sensing protocol (CLSP)/direct sequence (DS)-code division multiple access (CDMA) packet radio network (PRN) with adaptive packet length over burst-error correlated fading channels. CLSP controls the packet access in uplink of unslotted ALOHA/DS-CDMA systems so that contention is avoided and throughput is maximized. However, due to high uncertainty of radio channels, the performance of CLSP/DS-CDMA PRN may suffer from notable degradations. Using theoretical analysis and simulation, the authors show that in highly correlated fading environments adapting the length of radio packets to fading conditions significantly improves system performance and energy efficiency of mobile terminals. In their modeling, they study the relation between the fade statistics and the packet length in correlated Rayleigh fading channels. The effects of reception diversity, imperfect transmit power control (TPC), and user mobility are considered. The results are used to develop simple, energy-efficient, and robust adaptation mechanisms.     

A distributed media access protocol for packet radio networks and performance analysis. Part 1: Network capacity

A distributed time-slot assignment protocol is developed for a mobile multi-hop broadcast packet radio network, using time division multiple access channel access and virtual circuit switching. The protocol eliminates the single point failure mode of centralized network management and the delays of centralized processing. It is applicable to the user-to-user communications functions of such systems as the U. S. Army's enhanced position location and reporting system (EPLRS). The important functions of the distributed protocol, including time-slot assignment, virtual circuit set-up, and network synthesis, are identified, and implementing algorithms are presented and verified. The performance analysis of the protocol is divided into two parts. In this paper, Part 1 of the performance analysis, the capacity of a network using this protocol is studied and a tool is developed to design the network capacity by trading off among the network area, the transmission range, and the number of packet radio units. Since these results are not in closed form, numerical results provide insight into these parameters. In Part 2 the network set-up time and network data rate are analysed and a hierarchical architecture for the distributed protocol is proposed and analysed.     

Spatial reuse in multihop packet radio networks

Multihop packet radio networks present many challenging problems to the network analyst and designer. The communication channel, which must be shared by all of the network users, is the critical system resource. In order to make efficient use of this shared resource, a variety of channel access protocols to promote organized sharing have been investigated. Sharing can occur in three domains: frequency, time, and space. This paper is mostly concerned with sharing and channel reuse in the spatial domain. A survey of results on approaches to topological design and associated channel access protocols that attempt to optimize system performance by spatial reuse of the communication channel is presented.     

应答式干扰下基于Q学习算法的跳频系统信道调度方法

针对应答式干扰对跳频通信的影响,提出了基于Q学习算法的认知无线电跳频系统信道调度模型.该模型根据认知系统对跳频行为的实时回报评估值,运用机器学习的方法寻找出最合理的规避干扰策略,最终达到适应干扰的目的.运用Simulink对该干扰方式下的算法应用性能进行了仿真验证,结果表明该算法能够降低跳频系统此干扰下的误比特率到1%以下,基本接近未受干扰下的误比特率.     

An adaptive ISMA-DS/CDMA MAC protocol for third-generation mobilecommunications systems

An inhibit sense multiple access-direct sequence/code division multiple access (ISMA-DS/CDMA) medium access control protocol for a packet transmission mobile radio network is presented. The main feature of this protocol is its ability to retain the inherent flexibility of random access protocols while at the same time reducing to some extent the randomness in the access in order to increase the system capacity. In this framework, the protocol is presented together with some adaptive mechanisms that improve the protocol performance by means of regulating the access and varying the transmission bit rate according to the channel load that is broadcast by the base station. As a result, an adaptive bit rate algorithm is presented that reaches a throughput value close to the theoretical maximum     

基于nRF24L01和ESP8266的跳频及干扰演示实验

跳频是当今无线通信中的一个重要抗干扰手段。文章以WiFi模块ESP8266,nRF24L01无线模块和STM32F103单片机组成无线节点,设计多频率跳频及干扰演示实验。该设计在教学过程中不但能够直观地对跳频和干扰效果进行演示,而且因为靠近硬件层次编程,有利于引导学生学习单片机、WiFi网络以及无协议无线通信中的许多基本原理,较好地激发学生的学习热情。     

Design and analysis of an MAC-layer protocol for acar-to-infrastructure packet radio network

The structure of a packet radio network that must operate in an environment characterized by the presence of mobile stations and a ground network with fixed access points is defined. Each of these points consists of a ground station with a certain coverage area, which must exchange data with the mobiles over a common radio channel. Mobiles within the coverage area of a ground station must coordinate their access to the common channel. The design and analysis of the multiaccess protocol is considered, together with the procedure for the passage from a ground station coverage area to the next one along the direction of flow. The overall access strategy is described and analyzed to some extent, and simulation results are provided. The integration of this medium access control (MAC) layer protocol with existing packet radio software that also covers higher layer features is also discussed     

An urn occupancy approach for cognitive radio networks in DTVB white spaces

The paradigm of cognitive radio recently received considerable interest to address the so called ‘spectrum scarcity’ problem. In the USA, the Federal Communications Commission issued the regulatory for the use of cognitive radio in the TV white space spectrum. The primary objective is the design of cognitive devices able to combine the use of spectrum sensing and GEO-location information with the concept of the cognitive control channel to manage the cognitive devices. The recent standard ECMA-392 defines physical layer techniques and medium access control protocols to enable a cognitive network managed in a fully distributed fashion. In this work, we pursue the design of an efficient medium access control protocol for the cognitive control channel to flexibly and reliably exchange messages inside the cognitive radio network. In particular, we explore how the cognitive devices can raise their awareness of spectrum vacancies of spectrum vacancies by means of sensing when the distributed beaconing defined by ECMA-392 is used. Our main contributions are the following: (1) we propose a proprietary medium access control protocol based on the Standard ECMA-392; (2) we model the behavior of the cognitive radio network by means of an innovative urn model approach, (3) we investigate the access of the cognitive devices to the frequency channels with and without spoofing attacks and (4) we investigate the ability of the cognitive devices to identify frequency holes accounting for perfect and imperfect spectrum sensing, as well as we study the network throughput.     

Outage Probability in GSM-GPRS Cellular Systems With and Without Frequency Hopping

General packet radio service(GPRS) is designed for transmitting packet data andis supposed to take its radio resource from the pool ofunused channels of GSM voice services. Obviously, theintroduction of GPRS has an impact on the voice services.In this paper, we present a method to calculate theoutage probability of the GSM-GPRS network for bothnon-frequency hopping and frequency hoppingsystems. This method takes into account Rayleighfading, power control (with error), discontinuoustransmission, and frequency hopping (if applied). Theoutage probability of voice services affected by theintroduction of GPRS is discussed. The number ofunused voice channels allocated to GPRS depends on thedifference between the outage level of the existingGSM network and the maximum acceptable level. Thefrequency hopping system can accommodate more GPRStraffic than the non-frequency hopping system. Thepower control error has more impact on systemperformance when more channels are allocated to GPRS.Beyond our expectations, for the non-frequency hoppingsystem, the channels provided for GPRS are not muchdifferent between high channel occupancy and lowchannel occupancy of voice services. In contrast, for thefrequency hopping system, the system can provide morechannels for GPRS at low channel occupancy. The cellservice area decreases by about 10% 20% for eachadditional channel allocated to GPRS.     

Optimal Joint Session Admission Control in Integrated WLAN and CDMA Cellular Networks with Vertical Handoff

This paper considers optimizing the utilization of radio resources in a heterogeneous integrated system consisting of two different networks: a wireless local area network (WLAN) and a wideband code division multiple access (CDMA) network. We propose a joint session admission control scheme for multimedia traffic that maximizes overall network revenue with quality of service (QoS) constraints over both the WLAN and the CDMA cellular networks. The WLAN operates under the IEEE 802.11e medium access control (MAC) protocol, which supports QoS for multimedia traffic. A novel concept of effective bandwidth is used in the CDMA network to derive the unified radio resource usage, taking into account both physical layer linear minimum mean square error (LMMSE) receivers and characteristics of the packet traffic. Numerical examples illustrate that the network revenue earned in the proposed joint admission control scheme is significantly larger than that when the individual networks are optimized independently with no vertical handoff between them. The revenue gain is also significant over the scheme in which vertical handoff is supported, but admission control is not done jointly. Furthermore, we show that the optimal joint admission control policy is a randomized policy, i.e., sessions are admitted to the system with probabilities in some states     

New collision-channel model for packet-switched CDMA networks

Packet conflicts in a distributed CDMA network vary with different code protocols which determine packet structure. Improperly designed packet structure is responsible for unrecoverable packet collisions in the channel, resulting in an unacceptably small throughput and large delay. A novel collision-channel model is presented to analyse the network performance concerning the packet contention nature for different CDMA code protocols.<>